The invention relates generally to gripping tools and more particularly to an adjustable wrench suitable for use on six-sided fasteners.
Six-sided or "hex-head" fasteners such as screw heads and nuts are in wide use. Many hand-held devices have been developed over the years for use on six-sided fasteners. Principal among these wrenches are the adjustable wrenches which allow the user to utilize the same wrench for different size fasteners. Of the open end adjustable wrenches used on hex-head fasteners, the so-called "crescent" wrench is the best known. The crescent wrench has an open end between a fixed gripping head and another gripping head which is adjustable by a rotatable screw. One disadvantage of the crescent wrench when used on hex-head fasteners is that the gripping heads only bit two of the six sides. Another disadvantage is that the adjusting screw is oriented transversely to the longitudinal axis of the wrench handle, thereby causing the crescent wrench to have a large width adjacent to the gripping heads which may not conveniently fit a fastener because of obstructions located adjacent to the hex-head.
A number of problems are common to any wrench which only grips two sides of a polygonal fastener. Among these is a relatively "poor grip" which causes the wrench to slip which in turn causes rounding of the corners of the fastener. This problem is particularly troublesome where it is necessary to loosen a very tight or "frozen" fastener.
U.S. Pat. No. 183,266 to Jordan, U.S. Pat. No. 1,242,097 to Anderson and U.S. Pat. No. 3,358,533 to Wren disclose other mechanical arrangements in which two jaws close in on the fastener in order to grip it. Such arrangements eliminate some problems associated with the standard crescent wrench, but the fastener is still only gripped on two of its six sides. As a result, torque is being exerted on the fastener only at two opposite sides of the six-sided fastener. In Jordan and Wren, two additional sides of the fastener may come in contact with the wrench, however, if such contact is made there is only minimal force exerted by the wrench upon those two sides, and in any event that force is not equal to the force exerted on the fastener by the two jaws. Any such additional unequal force exerted on the fastener will not provide markedly improved grip nor will it alleviate the problem of rounding edges.
U.S. Pat. No. 3,670,604 to Fronell discloses a wrench which grips the hex-head fastener on three sides. Fronell, however, does not disclose an open end wrench but rather discloses a spanner which must completely surround the fastener. In U.S. Pat. No. 433,358 to McCarthy, a wrench is disclosed that utilizes two extending arms with gripping heads. McCarthy, however, is only concerned with improvements in the strength and adjusting mechanism of a wrench and not with any special gripping configuration which makes the wrench more useful on six-sided fasteners.
It is therefore a principal object of the invention to provide an adjustable wrench which will reliably grip a six-sided fastener with enhanced force.
Another object of this invention is to provide a tool of this kind that is easily and quickly adjusted to different size hex-head fasteners.
Still another object of this invention is to provide a tool of this kind that can be used for tightening and loosening the hex-head without changing the user's grip on the tool.
Another principal object of this invention is to provide a wrench structure with adjustable jaws whose adjusting mechanism is arranged so that there is a low level of strain on the adjusting mechanism while the wrench is in use.
Yet a further object of this invention is to provide a tool of this kind that is simple and rugged in construction, efficient for the purposes intended and easy to manipulate.